1282 THE BELL SYSTEM TECHNICAL JOURXAL, XOVEMBER 1954 



Taking the derivative of w with respect to /x gives 



^ = __Gd_ 

 dn 2wMm2 



where M = 'Imrrob. For the fly-bar governor, dco/dij., is as follows from 



(11) 



CO = q = /j/' 



G{d - nc) + MfjLOJo'^ 



Mfx 



(12) 

 Sco ^ __Gd_ 



dn 2coikf/i2 



Since the equations are identical for both governors the same considera- 

 tions exist in holding to a minimum the change in speed caused by a 

 change in the coefficient of friction. 



For optimum speed regulation, the partial derivative, du/d^, should 

 be a minimum. Small values of du/dn can be obtained by operating on 

 the design constants, controlling the value of n, or ha\'ing high governor 

 speeds. Specifically, the design constants m, ro, r and h should all be 

 large. Inspection of the drive-bar governor schematic. Fig. 4, shows that 

 there are physical limitations to the arbitrary enlargement of these 

 values. Space, manufacturability, and cost of materials must be consid- 

 ered in establishing these terms. In selecting materials for fixing the 

 coefficient of friction value the wearing quality of the materials to be 

 used must be of first consideration. A high governor speed is advantage- 

 ous but must be weighed against the primary disadvantage of high inertia 

 loads for the entire mechanism. 



The temis G and d in the numerator of equations (11) and (12) indicate 

 that low input torque and a small value for d would be desirable For G, 

 one must consider the anticipated change in dial efficiency and variation 

 in torque produced by the pulsing mechanism plus the torque necessary 

 for the governor to maintain adequate speed control. 



As shown in the drive-bar governor schematic. Fig. 4, d is the dis- 

 tance from the weight pivot to the noraial of the point of contact be- 

 tween the rubber stud and governor case. Its magnitude is controlled by 

 the stud angle a, and the distance between the stud and case when the 

 weights are in the closed position. 



As indicated, d should be as small as possible for best regulation with 

 friction change. This requirement imposes a difficult design problem 

 because as d decreases, the stud and bearing hole in the weight approach 



